The present invention relates in general to the design and construction of a blow-molded, plastic paint container having a threaded, screw-on cap. More specifically, the present invention relates to the design and construction of a paint container that includes a screw-on cap design with means to sever an interior paint skin extending between the inner surface of the cap and the inner surface of the container body. In a related embodiment of the present invention, the screw-on cap includes a partitioning wall that causes any paint skin to form in two separate portions, one associated with the cap and one associated with the container body.
Many paints are prone to exhibit a “skinning” effect when exposed to air, wherein a firm skin forms over the softer or less viscous “under” paint. While the skinning effect can be seen in oil paints on a palette, it is also common with interior and exterior house paints, whether oil-based or latex. When a conventional one gallon can or container of house paint is opened for use and then resealed after use by tightly pressing the lid back into the receiving groove, air becomes trapped inside. This trapped air contributes to the formation of a skin over the remaining paint in the container. When the container is re-opened for use, the skin needs to be removed so that it is not dispersed into the paint. If the skin is dispersed into the paint, it can be applied to the painted surface and thereby adversely affect the finished quality in terms of smoothness of the paint on the surface. As a result, some devices have been offered to try and eliminate, or at least lessen, the skinning effect. Various techniques or methods of use have also been proposed to eliminate or lessen the skinning effect.
Understanding the skinning effect and what occurs when paint containers are initially opened and then sealed closed has prompted consideration by paint companies and container manufacturers of what occurs when paint containers are initially filled and sealed closed. Considering the range of container sizes, often ranging from one gallon to one quart, and considering the material options, such as various metals and various plastics, does a skin form over or around the paint as received from the manufacturer or filler?
While it is possible to have some small amount of air trapped in the paint container as it is being initially filled and sealed closed, any skinning would be expected to be minimal. However, in an attempt to hopefully eliminate any risk that any paint skin that does form will not be dispersed into the paint, the inside surface of the lid for many metal, one-gallon paint containers includes a surface texturing or coating. This texturing or coating causes the skin (of the paint) to adhere to the lid. As a result, when the lid is removed, the skin portion that is adjacent the lid is also removed and is therefore not at risk for falling off or dropping back into the paint container. While such surface texturing or coating may be a viable option for metal containers when considering the style and configuration of the metal lids and how those lids seal the container closed, a question was raised as to whether these same techniques would be suitable for plastic paint containers, and particularly those having screw-on lids or caps, such as one-quart, blow-molded, plastic paint containers. The present invention addresses this question.
The present invention is directed to a one-quart, plastic paint container with an internally-threaded, screw-on cap. While this represents the preferred embodiment of the present invention, it should be noted that the invention embodiments disclosed herein would be applicable to virtually any type or size of paint container having a screw-on cap. The present invention would presumably also be applicable to containers for any other substance that demonstrates a similar likelihood for skinning.
In studying the known technology used for metal paint containers with metal lids, the present inventors discovered that a rough surface, polyfoam liner assembled into the plastic cap causes the paint to adhere to that liner, similar to what occurs with a coated metal lid. Ideally, when the cap is first removed, any paint skin that may have been formed adjacent to the cap would come off with the cap, adhering to the liner, and therefore not break up or fragment such that portions of the paint skin would fall off or drop back into the paint in the container.
What has been discovered by the present inventors is that the current design of the one-quart, blow-molded plastic paint container has a small head space that allows a paint skin to form adjacent the inside of the container and adjacent the inside of the cap or lid. When the cap is initially removed (unscrewed), the paint skin that laps over the container-to-cap interface can tear and paint skin fragments can break off and drop back into the paint container. This becomes a second problem to solve, the first problem being the selection of a suitable coating or a liner for the cap in order to get some portion of the paint skin to adhere to the cap. Using a cap liner to which the paint skin adheres captures a portion of the paint skin, lessening, but not necessarily eliminating, the chances of skin fragments breaking off and dropping back into the paint.
The present invention solves this second problem in a novel and unobvious way by adding a dividing or partitioning wall as part of the cap such that the paint skin forms in two separate portions, one on each side of the partitioning wall. One paint skin portion adheres to the cap liner and is removed intact with the cap. The other paint skin portion adheres to the inner surface of the container body and remains intact with the container body wall.
In a second embodiment of the present invention, the partitioning wall is replaced by a set of equally-spaced cutting blades. Since there are open spaces between these cutting blades, the paint skin is formable through these spaces, extending from the liner to the container neck opening. While the paint skin still adheres to the liner and to the inner surface of the container body, the portions of the paint skin that extend through the clearance openings between adjacent cutting blades need to be severed and this is the function of the cutting blades as the cap is unscrewed.
In this way, the paint skin portion that adheres to the cap remains with the cap and the paint skin portion that adheres to the container body remains with the container body. These two paint skin portions stay adhered to their corresponding packaging portions and do not fragment, break up, or peel off and drop back into the paint.